Realistically if you are writing an indie miniatures game you are writing for people that are already veterans of the hobby and know "how it works". I don't think it is a good idea to always take that for granted however. First and foremost it obviously discourages new players from picking up the game. Yes, the prospective new player isn't likely to go to Wargame Vault first instead of just picking up some Warhammer or Bolt Action boxes at the local store but that doesn't mean nobody will.

Second, I think it can encourage poor writing because we get into a habit of relegating more and more features to "how it works". 

Recently I was reading through a set of skirmish rules and realised that at no point did it explain how casualties were actually removed from the unit. It could be implied based on the game it was inspired by, but it never actually clearly stated it. Does that matter? In a game where some figures can have a heavy weapon it matters quite a bit. It also tends to come up when it comes to keeping units out of close combat range (or within it). 

For an example that has become a bit of a catch-phrase with my friends, someone told me about a game that did not actually explain exactly how charging an enemy worked. They sent an email to the writer of the game who replied that you charge in the usual way.

Indeed. 

When you are writing rules try to develop a critical eye for the step by step of the process. You may be surprised to find that there are more steps than you thought and some of them may benefit from being made explicit. 

As an example does it matter who rolls the dice for something? Most of the time it does not and you won't have to say anything but what if the game system features a pool of reroll points that a player can use any time they roll the dice for anything? Now it does matter if I roll for the armour saves or if you do.

A few pain points that I find are easy to miss (and have missed in the past!):

* How are measurements done from figure to figure?

* How exactly does rerolls work?

* How are casualties removed in games with multi-figure units?

* Can I pick any target when I shoot?

* Can figures move through other friendly figures?

* What is stopping me from just shooting at that officer over there? 

* If multiple things are happening at the same time, how do we figure out how they get resolved? 

I am sure you can think of many more when you sit down and look critically at a set of rules. Give it a try.